The present invention relates to environmental control and monitoring of buildings, and more particularly to systems for controlling and monitoring heating, air conditioning, lighting, security, occupancy, and usage of distributed facilities such as hotels and the like.
The control of distributed systems such as building systems has been undertaken in connection with commonly used computer networks and business software. See, for example, U.S. Pat. No. 4,212,078 to Games et al. A major difficulty with such systems is the expense of wiring interconnections between elements of the system, particularly when there are additions or changes to be made in the system. The expense of these interconnections can be reduced somewhat by the use of efficient network protocols, such as the widely known Ethernet standard that has a range of up to 1000 meters. Another recent development is the use of AC power wiring to transmit RF communications to remote controllers, such as disclosed in U.S. Pat. No. 4,429,299 to Kabat et al. A further development is control using a combination of wired and wireless communications as disclosed, for example, in U.S. Pat. Nos. 5,440,301 to Evans and 5,476,221 to Seymour.
Unfortunately, centralized wireless control systems for building appliances have not been widely utilized, largely because systems having sufficient range normally are subject to regulations and licensing requirements that are prohibitively expensive. Also, systems that are sufficiently powerful to be used in widely distributed installations are unnecessarily expensive in smaller installations. Further, there is limited availability of RF carrier frequencies, and potential interference with other nearby systems that might be operational.
Thus there is a need for a wireless appliance control system that overcomes the disadvantages of the prior